Apparatus for examining electrochemical effects of in vivo metal implants causing allergic symptoms and/or inflammation in a living organism

ABSTRACT

An apparatus for examining the electrochemical effects of (in vivo) metal implants causing allergic symptoms and/or inflamation in living organism, the apparatus containing two probes and a signal processing circuit connected thereto. One of the probes is a reference electrode (1) provided with reference electrolyte (34), which is connected to the soma tissue near the implant while the other probe is a measuring electrode (2) provided with a metal contact tip (6) to be contacted with the implant. The reference electrode (1) and the measuring electrode (2) are connected through an amplifier (20, 27) to one of the inputs of a comparing unit (22, 28). The other input of the comparing unit (22, 28) is connected the output of a memory (24, 30) containing data concerning the metal to be examined, and one of the outputs of the comparing unit (22, 28) is connected the display for the measured data (11).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus for examining the electrochemicaleffects of in vivo metal implants causing allergic symptoms and/orinflammation in a living organism.

2. Description of the Related Art

Recent research has demonstrated that metal implants in living organismcan cause allergic symptoms as a result of ionic migration from themetal alloys implanted in vivo toward the living tissues. These migratedions easily connect to protein bodies at the temperature of the humanbody. As a result, in the organism already implanted with metal,allergic symptoms can appear, i.e. local or long-distance mucosal andcutaneous reactions, eczema, dermatitis, dermatosis, etc. Under certaincircumstances, this effect can cause extraordinary serious altercations,and the risk exists until the anaphylactogemic factor, i.e. the metalimplants which can be dental prosthesis, filling of a tooth, screw,nail, etc., is removed from the organism.

HU-PS 192 218 describes a method and apparatus for exploring andexamining such effects. By use of the mentioned apparatus and method,potential difference is measured between the implanted metal alloys and,at the same time, ion currents effected by the potential difference aremeasured in vivo in the neighboring soma tissues. For making themeasurement, a specially formed measuring probe is applied, the currentvalues are measured by a current/potential (I/U) converter connected tothe measuring probe, and by a signal processing unit connected thereto,then displayed.

It has been found in practice that during the application of thementioned known apparatus, the ion migration causing the harmful effectscannot be explored to the extent necessary. During the application, ithas been also demonstrated that the measured values cannot be reproducedconsistently, and that the measurements obtained are influenced bynumerous parameters and by chance as well. Also, the measuring unit isembedded in a relatively large instrument case, so that its applicationbecomes difficult. A further problem is that more than one person isrequired to perform the measurement, to accomplish suitable location ofthe probes and their connection, and for reading the measured values onthe instrument.

WO 89100400 describes a solution where the reference electrode isintegral part of the apparatus and, as such, the reference electrodecannot be releasably connected to the apparatus. Neither the referenceelectrode, nor the measuring electrode can be made as a disposablearticle.

A further serious disadvantage of both mentioned solutions is to meetthe requirements of hygienic regulations, which, considering thespreading of the newer epidemic-like diseases, become increasinglystrict with respect to handling of instruments and apparatuses usedduring medical treatment. In the case of this known solution, thesterilization of the apparatus embedded in the instrument cannot beoperated in accordance with the regulations.

SUMMARY OF THE INVENTION

The aim of the invention is partly to eliminate the disadvantages of thementioned known solutions and partly to develop an apparatus, which, onthe one hand, performs the electrochemical examination of the metalimplants in vivo more accurately and reliably, and on the other hand,the apparatus processing the measured data can be handled easily andmeet all the requirements of the latest hygienic regulations as well.

In electrochemistry, it is well known that every metal and every metalalloy can be determined by the so called anodic polarization curve. Onthe basis of that curve, it can be seen on which potential no metaldissolution can be found in given medium, the potential value abovewhich chloride containing solution pitting corrosion attack begins, andwhere the metal dissolution is expected. Thus, in the case of the metalsas well as metal alloys used for metal implants, the anodic polarizationcurve provides an indication of which cases an undesirable effect canoccur.

The invention is based on the recognition that if the potentialdifference is measured not between two metal implants in vivo, butbetween a metal implant and a reference electrode palpating theneighboring soma tissue, so that there is no need for measuring thecurrent, more accurate, more reliable and predictably reproduciblemeasurements can be obtained. For each case of applying metal or metalalloy, the corrosion potential can be determined, and the range can bepredetermined, within which, pitting corrosion or metal dissolution canoccur.

The essential recognition is in that taking into consideration onlyrecent dental practice, several kinds of new materials have beenappeared, for which it cannot be known exactly whether they have ananaphylactogenic effect or not, because neither the measuring methodapplied up to now, nor its accuracy enables this knowledge.

The main task to be solved by the invention is an apparatus forexamining by potential measuring the electrochemical effect of theimplanted metal substitutions (in vivo) causing allergic symptoms and/orinflammation in the living organism.

The potential difference is measured between the implanted metal and thereference electrode palpating neighboring soma tissue.

The measured potential difference is compared with the corrosionpotential values, obtained in vitro for the metal implants and it isalso preferred according to the invention, if it is determined that apotential difference concerning the given metal is higher than apredetermined limit value indicating the initial stage of thedissolution of that metal.

It is also advantageous, if light or sound signal indicate if thepotential difference higher than the limit value.

Besides the above, it is preferred that if before the finalimplantation, a sample of the same implant-material to be implanted, iseither contacted to the implantation place to be expected or arrangedthere expediently for a period of 24-28 hours, and then the potentialdifference is measured.

The object of the invention is an apparatus for examiningelectrochemical effects induced by in vivo metal implants that may causeallergic symptoms and/or inflammation in a living organism. Theapparatus comprises a reference probe having a reference electrode and areference electrolyte, a measuring probe having a measuring electrodeprovided with a metal contact tip, a signal processing circuit connectedto the reference and measuring probes and including an amplifier, acomparing unit having two inputs and an output, a memory for storingdata concerning the implanted metal and having a memory output, and adata display, one of the two inputs of the comparing unit beingconnected to the amplifier, the other of the two inputs of the comparingunit being connected the memory output, and the output of the comparingunit being connected the data display.

The reference probe comprises a handle and an axially aligned headpiecehaving opposite ends. The headpiece is connected releasably at one theopposite ends to the handle through an electric contact on the handleand connected to a line connected to the amplifier. The other of theopposite ends of the headpiece supports a plastic tube containingelectrolyte, an absorbent element impregnated with the electrolyte isarranged in the plastic tube and protrudes from the plastic tube as thereference electrode, and a the metal part in the headpiece connects theelectrolyte in the plastic tube to electric contact on the handle. Themeasuring probe includes a measuring headpiece having opposite ends, oneof the opposite ends is connected releasably to a measuring handlethrough an electric contact associated with a start switch in themeasuring handle, and a metal contacting tip projects from the other ofthe opposite ends of the measuring head piece.

Preferably, the headpiece of the reference probe includes an electrolytetank and the plastic tube has one end protruding from the tank, anopposite end located in the electrolyte tank at a distance from themetal part, and a separating layer covering the opposite end. The metalpart includes an electrically non-conducting pricking element topenetrate the separating layer.

It is advantageous, if the head element of the reference probe isprovided with a lock cap.

In a further preferred embodiment according to the invention, theheadpiece is provided with a cover.

It is advantageous in the sense of the invention if the headpiece andthe handle are connected to each other by bayonet joint or the headpieceand the handle are connected to each other by breaking joint.

In a further preferred embodiment according to the invention theheadpiece is disposable.

It is advantageous if the electrolyte is of colloidal get state.

It is advantageous finally if the measuring apparatus is embedded in adental column.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail with the aid of the encloseddrawings presenting the embodiment of the solution according to theinvention by way of example, in which:

FIG. 1a is a cross-section illustrating a possible embodiment of thereference electrode according to the invention for palpating the tissueconnected to the apparatus;

FIG. 1b illustrates an other embodiment of the headpiece of thereference electrode in section according to the invention for palpatingthe tissue,

FIG. 2 shows an embodiment of the measuring electrode also in section;

FIG. 3 is a block diagram of a possible embodiment of the apparatusaccording to the invention;

FIG. 4 is a block diagram of another possible embodiment of theapparatus according to the invention; while

FIG. 5 is a block diagram showing a further possible embodiment of theapparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1a illustrates in section a possible embodiment of a referenceelectrode 1 according to the invention for palpating the tissue, whichis connected to the measuring instrument 40 according to the invention.The reference electrode 1 has two main parts, i.e. a handle 16 and aheadpiece 19, which are releasably connected to each other and placed ina mantle-like cover. The measuring instrument 40 is connected to thehandle 16 containing a conductive line 15 connected between themeasuring instrument 40 and an electric contact 17 for connection of theline 15 to the headpiece 19. The contact 17 can be, for example, aspheroidal element supported by a spring 59 in a groove 58 formed in thehandle 16.

The head piece 19 is provided with a metal contact 18 for connectingelectrically to the spherical contact 17 on the one hand, and, on theother hand, with an electrolyte 34 provided in a tank 43. Theelectrolyte is saturated salt solution, i.e. NaCl solution, preferablyin a gel state. In the electrolyte 34, on the symmetrical axis of theheadpiece 19, is an insulated tube 33 containing a cloth-like absorbentor wick element 44 for absorbing the electrolyte 34. Preferably, theelement 44 extends from the projecting end of the tube 33 through apaper coot protruding from the tube 33 as a head element 36 forpalpating tissue. On the end of the tube 33 facing the contact 18 is aseparating layer 38 for separating the tube 33 from the electrolyte 34.At a given distance from the separating layer 38, and between theseparating layer 38 and the metal part 18, an electricallynon-conducting--insulating--pricking element 39 is arranged so that itstip faces in the direction of the separating layer 38. The tube 33 ismounted in the headpiece 19 by a joining element 41 so that it is ableto move in it axially in response to pressure. The joining element 41can be filled for example by sterilized air. One part of the tube 33also protrudes on the mantle-like cover 46 of the headpiece 19. Thus,the electrolyte 34 is absorbed into the tube 33 at all times. In orderto observe the absorption of the electrolyte 34, it is preferred thatthe electrolyte is mixed with an electrically non-conducting indifferentcolor material 37. In this way, the coloring of the protruding part ofthe tube 33 indicates the absorbing of the electrolyte 34 for thedoctor, which is the condition required for the electric conduction.

The headpiece 19 is provided with a cover 45 enabling it to be insulatedfrom the surroundings under sterilized circumstances up to the time ofutilization. The headpiece 19, itself, is disposable, that is, after useit can be throw away. To this end, the headpiece 19 and the handle 16are joined releasably to each other either by threaded connection, orbayonet joint, or simply by a breakable joint. This embodiment ispreferred because, in the examination by a dentist, the headpiece 19contacts the oral cavity of the patient. During the measurement, thereference electrode 1 should contact with the soma tissue, for example,with the mucosa of the patient. It is considered as a referencecondition, i.e. that the measurements could be reproduced. According tothe experience, the mucosa or other soma tissues can be considered as astable measuring point.

FIG. 1b illustrates another embodiment of the headpiece 19 in section,wherein the plastic tube 33, the tank 43 containing the electrolyte 34,as well as the absorbent element 44 are formed as a single element, i.e.in the tube 33, an absorbent element 44 impregnated with the electrolyte34 is arranged. This embodiment is extraordinarily simple, and theplastic tube prevents evaporation of the electrolyte 34.

FIG. 2 shows also in section, an embodiment of the measuring electrode 2for contacting metal applicable to use of the measuring instrument 40according to the invention. The measuring electrode 2 should becontacted with previously dried metal implants, for example, anover-denture in the mouth. The measuring electrode 2 also has two parts,i.e. a headpiece 4 having a contact probe tip 6 and a handle 5 connectedreleasably to each other, and they are embedded expediently in acylindrical case. The handle 5 contains a line 3 for joining to themeasuring instrument 40 and forwarding the measured signal, an electriccontact 9 ensuring the connection of the line 3 to the headpiece 5, anda line 14 provided with a start switch 7. The contact 9 can be aspheroidal element, for example, which is resiliently supported by aspring 60 in a groove 61 formed in the handle 5. The electrical contact9 is arranged coaxially in the handle 5. The headpiece 4 contains acylindrical lock-cap 8, on the end of which facing towards the handle 5,a metal contact element 10 is centrally formed, one side of whichtouches the contact 9. On the other side of the contact element 10, ametal contact tip 6 is provided, which is hermetically sealed, insterile way by the lock cap 8. In this way, the headpiece 4 can beformed as a disposable element as well, and the measurement can beperformed while excluding the possibility of infection.

The possible embodiments shown in FIGS. 1a, 1b, and 2 can be appliedexpediently for dental and dental surgery purposes. For the examinationof the effects induced by other metal implants, further embodiments canbe realized. For examination of metal implants in the body, the metalcontact tip 6 should be formed to the appropriate length and formationfor the applicable conditions. Similarly, the head element 36 of theheadpiece 19, for palpating the tissue, should be formed also inconformance with the soma tissue to be measured.

In the case of a possible embodiment of the evaluating measuringinstrument 40 in which the reference electrode 1 is arranged in thehandle 16, the result of the measurements is indicated on a display 11,either a visible LED display, for example, or an audible sound signal,while the reference values are shown on the alphanumerical display. Inaddition, the measuring instrument 40 is provided with a switch element13 for intermittent operation as well.

The arrangement itself can be formed so that the measuring instrument isembedded into a separate measuring case or into the column of the dentalchair. In this latter case, however, it is preferred that the display 11is an alphanumerical display 12 or is formed with the headpiece 16 ofthe reference electrode 1 or as a unit with the headpiece of themeasuring electrode 2.

The measuring instrument 40 itself can be realized with both analogueand digital circuits.

In FIG. 3 a possible embodiment of the measuring instrument 40 is shownwith digital circuits. The line 15 of the reference electrode 1 forpalpating the soma tissue, and the lines 3 and 14 of the measuringelectrode 2 contacting the metal implants provide means for passingmeasured potential difference is through the amplifier 20, the output ofwhich is connected to the input of the A/D converter 21, the output ofwhich, in turn, is connected to one of the inputs of the comparing unit22, while to the other input of the comparing unit 22, the output of themultiplexer 23 is joined. The output of the comparing unit 22 is coupledwith the display 11 on the one hand, and on the other hand with one ofthe inputs of the switch control circuit 25. The inputs of themultiplexer 23 are connected to the outputs of the memory 24 while itscontrol input is joined to one of the outputs of the switch controlcircuit 25. The so-called dangerous potential values concerning themetals and metal alloys to be examined are fed in the memory 24. Theselection of the data relating the metal or metal alloy just examinedtakes place by the aid of the switch control circuit 25, the other inputof which is coupled with the switch element 13. The limit values are setup in the memory 24 to correspond to the potential considered asharmful, which exceeds, for example, the positive value of +150 to +200mV at the corrosion potential for Ni-based alloys. Naturally, the limitvalue can be determined for all the metals even in the case where thereference electrode 1 is made of other material. One output of theswitch control circuit 25 is connected to the input of the memory 26,the output of which is joined to the input of the alphanumerical display12.

FIG. 4 represents the possible embodiment of the measuring instrument 40according to the invention, which is realized by analogue circuits. Theline 15 of the reference electrode 1 palpating the soma tissue, and thelines 3 and 14 of the measuring electrode 2 palpating the metal, measurethe potential difference through an amplifier 27, the output of which isconnected to one of the inputs of the comparing unit 28, while the otherinput of the comparing unit 28 is joined to the output of themultiplexer 29. One of the outputs of the comparing unit 28 is connectedto the display 11, while its other output is joined to one of the inputsof the switch control circuit 31. The inputs of the multiplexer 29 areconnected to the outputs of the analogue memory 30, while its controlinput is joined to the other input of the switch control circuit 31. Thepotential data value concerning the metals and metal alloys to bemeasured and considered as dangerous, are fed in the memory 30. Theselection of the implant to be measured is taken place by the switchcontrol circuit 31, which is coupled with the switch element 13. Theindividual limit values are set in the memory 30 on the previouslydescribed way. One output of the switch control circuit 31 is alsoconnected to the input of the memory 32, the output of which is led tothe input of the alphanumerical display 12. It is expedient, firstly tokeep in view the shock-proof prescriptions, secondly for the sake ofsimple handling, to utilize some kind of battery as power supply unit.

A further possible embodiment of the measuring instrument 40 accordingto the invention can be seen on FIG. 5.

The line 15 of the reference electrode 1 and the lines 3 and 14 of themeasuring electrode 2 are connected to the input of the amplifier 50having high input resistance, in order to join the direct currentvoltage (D.C. voltage) coming from the reference electrode 1 and themeasuring electrode 2 to the input A/D converter of the processor 51connected to the output of the amplifier 50. The input points areexpediently provided with diode protection. The applied amplifiers areformed with low noise levels and low drift circuits. To the output ofthe processor 51 is joined the display 55, expediently LCD display, oneof its control inputs is connected to the operation mode switch 54,while its other input joins to the supply unit 56, its further input-,output channel is connected to the memory field 53 and a RS 232 port 57.The processor 51 is in conjunction with the reference voltage source 52as well.

The task of the latest embodiment, is to ensure the requestedtemperature for the A/D conversion as well as the reference potentialvalues being independent from supply voltage. The task of the memoryfields 53 is to store the operating program and potentials in tableform. The measured values are written in EEPROM. The measured valueswith serial numbering are stored or in a given case, together with apreselected international tooth identification or other identificationnumber as well. Each identification number contains the data of tooth orof an interior organ, of the material of implants and that of the dataconcerning the limit potential. The task of the operation switch 54 isto put into operation the apparatus, to select the given potential limitvalue and to start the measuring. The display 55 displays the set andmeasured value.

During the measurement, firstly the reference potential concerning theimplants to be measured is selected by means of either the switchcontrol circuit 31 or the operation mode switch 54, then the referenceelectrode 1 is pressed onto the soma tissue near the implant to bemeasured, observing that the electrolyte 34 is absorbed in the absorbentelement 44, respectively. In the case of the embodiment wherein thereference electrode 1 is provided with a headpiece 19 impregnated withelectrolyte 34, it is simply pressed onto the soma tissue. Then themeasuring electrode 2 is pressed onto the metal implant to be measuredand the potential difference between the reference electrode 1 and themeasuring electrode 2 is measured.

If the measured value considering the characteristic corrosion potentialof Ni-based alloys shows a difference of about from +150 to +200 mV,then it is considered as pathologic in the case of the referenceelectrode 1 of Ag/AgCl. The potential values can be determined by knownway for every metal or metal alloy.

The solution according to the invention can be applied advantageously,for example, in the dental practice for both diagnostic and prognosticpurposes as well as in the surgery before implanting the implant. By theaid of this, it can be examined whether the over-denture can causeallergic or inflamation symptoms, or it can be determined beforeimplanting the implant whether it can cause problems in the future.

We claim:
 1. Apparatus for examining electrochemical effects induced by in vivo metal implants that may cause allergic symptoms and/or inflammation in a living organism, comprising:a reference probe having a reference electrode and a reference electrolyte; a measuring probe having a measuring electrode provided with a metal contact tip; a signal processing circuit connected to the reference and measuring probes and including an amplifier, a comparing unit having two inputs and an output, a memory for storing data concerning the implanted metal and having a memory output, and a data display, one of the two inputs of the comparing unit being connected to the amplifier, the other of the two inputs of the comparing unit being connected to the memory output, and the output of the comparing unit being connected the data display to provide an indicated comparison of measured value with data stored in the memory; wherein the reference probe comprises a handle and an axially aligned headpiece having opposite ends, the headpiece is connected releasably at one of the opposite ends to the handle through an electric contact on the handle and connected to a line connected to the amplifier, the other of the opposite ends of the headpiece supports a plastic tube containing the reference electrolyte, an absorbent element impregnated with the reference electrolyte is arranged in the plastic tube and protrudes from the plastic tube as the reference electrode, and a metal part in the headpiece connects the reference electrolyte in the plastic tube to the electric contact on the handle, and wherein the measuring probe includes a measuring headpiece having opposite ends, one of the opposite ends is connected releasably to a measuring handle through an electric contact associated with a start switch in the measuring handle, and the metal contact tip projects from the other of the opposite ends of the measuring head piece and is connected to a line connected to the amplifier.
 2. The apparatus of claim 1, wherein the headpiece of the reference probe includes an electrolyte tank and the plastic tube has one end protruding from the tank, an opposite end located in the electrolyte tank at a distance from the metal part, and a separating layer covering the opposite end, and wherein the metal part includes an electrically non-conducting pricking element to penetrate the separating layer.
 3. The apparatus of claim 1, wherein the absorbent element arranged in the plastic tube and protruding from the plastic tube as the reference electrode is provided with a lock cap.
 4. The apparatus of claim 1, wherein the headpiece of the reference probe is provided with a cover.
 5. The apparatus of claim 1, wherein the headpiece and the handle of the reference probe are connected to each other by a bayonet joint.
 6. The apparatus of claim 1, wherein the headpiece and the handle of the reference probe are connected to each other by a breaking joint.
 7. The apparatus of claim 1, wherein the headpiece of the reference probe is disposable.
 8. The apparatus of claim 1, wherein the headpiece of the measuring probe is disposable. 